1. Field of the Invention
The present invention relates to an urging structure for an output shaft of a drive motor, and more particularly to an urging structure for an output shaft of a small drive motor such as a carriage motor which is used for driving a pickup of a CD player.
2. Description of the Related Art
In a conventional CD player, as shown in FIG. 6, a turn table 2, a carriage 3, and the like are disposed on a chassis 1. The carriage 3 holds an objective lens 7 of a pickup in a center area thereof, and is placed in a center opening 1a of the chassis 1 so as to be movable in the anteroposterior direction (the direction along which the carriage approaches or separates from the turn table, and which corresponds to the vertical direction in the figure).
Guide shafts 8 and 9 serving as guide members for guiding the carriage 3 in the anteroposterior direction are disposed on both sides (the left and right sides in the figure) of the movement space for the carriage in the center opening 1a of the chassis 1. One of the guide shafts, i.e., the guide shaft 8 is configured by a round bar. The other guide shaft 9 serves also as a screw shaft. The guide shaft 9 is rotated by a carriage drive motor 11 which is fixed onto the chassis 1 via a bracket 10. The guide shaft 9 and the output shaft 11a of the motor 11 are drivingly coupled to each other via a gear train configured by a driving gear 12, two intermediate gears 13, and a driven gear 14.
The driving gear 12 is fixed to the output shaft 11a of the motor 11, the intermediate gears 13 are pivotally supported by a movable member which is not shown, and the driven gear 14 is fixed to the guide shaft 9. When the carriage drive motor 11 is activated to repeatedly rotate the guide shaft 9 in forward and reverse, the carriage 3 reciprocates in the anteroposterior direction on the chassis 1 along the guide shafts 8 and 9, so that the objective lens 7 on the carriage 3 radially crosses a disk which is placed on the turn table 2, and which is not shown.
In order to ensure that the carriage 3 is quickly moved, the carriage drive motor 11 is rotated at a high speed of, for example, 12,000 rpm. This causes a problem in that the driving noise produced when the motor operates is bothersome. In order to reduce the driving noise level, the exposed basal portion of the output shaft 11a is directly urged (laterally pressed) by an urging spring in a direction perpendicular to the axial direction of the shaft. When this urging is conducted, the operation noise level in operation of the carriage drive motor 11 can be reduced by several decibels (db) as compared with the case where such urging is not conducted.
Since the exposed basal portion of the output shaft is directly urged by the urging spring, the urging force is large, and hence the load on the output shaft is increased so that the starting voltage is required to be high. This causes a problem in that the carriage cannot be finely motor-controlled at a low voltage.